Diseases characterized by endothelial (EC) injury are a major cause of surgical morbidity and represent a significant public health problem. They include post-traumatic inflammatory and infectious syndromes, such as systemic inflammatory response syndrome (SIRS), multiple organ dysfunction (MOD) and acute respiratory distress syndrome (ARDS). Preliminary studies suggest that phosphorylation and dissociation of endothelial adherens junctions, combined with endothelial retraction, may represent the final common pathway for mediators that cause EC barrier dysfunction. Less clear are the mechanisms that lead to junctional phosphorylation and dissociation, including the role of oxidants, rho pathways, MAPK and Src kinases. Our objective is to identify the dominant pathways that regulate junctional dissociation and EC retraction. Major experimental problems include understanding the enzymatic source of intracellular oxidants and their role in junctional phosphorylation, and determining the role of the cytoskeleton in EC retraction during regulation of EC barrier function. Our central hypothesis is that EC oxidant production induced by tumor necrosis factor-alpha (TNF) ultimately results in tyrosine phosphorylation of adherens junction proteins and EC retraction; both events together weaken the adherens junction, causing junctional dissociation and intercellular gap formation. The overall objectives are to determine the role of intracellular oxidants, rho and MAPK pathways on junctional phosphorylation and endothelial dysfunction. [unreadable] [unreadable]